Max-width problem with Opera

Works fine in Mozilla

[TheDoctor]

My site contains, amongst other things, pages that include short academic papers or the like (one article, summary or abstract per page). In each case, the first paragraph is displayed in a larger font than the rest of the article.

Convinced by an earlier thread in this forum that spreading the text across the screen when the user is viewing the page in a large window makes the page less than fully readable, I put a max-width into my CSS. The CSS thus came out more or less like this (irrelevant stuff omitted):

.lead { font-size: 110%; }
.paper p { max-width:40em; 
 margin-left:auto;
 margin-right:auto; }
.paper p.lead { max-width:36.364em; }

This works fine in Mozilla, with the text nicely lined up in the middle of the screen, the lead text being the same width as the text in the rest of the article.

However, in Opera, the lead paragraph is slightly less wide than the other paragraphs. To get it to be the same width, I have to define max-width of the lead paragraph as 37em, which makes it wider than the main text when viewed in Mozilla.

Same problem, BTW, with

.lead { font-size: 110%; }
.paper p { max-width:39.6em; 
 margin-left:auto;
 margin-right:auto; }
.paper p.lead { max-width:36em; }

Has anyone seen this before? Any idea(s) about a workaround?

[TheDoctor]

<bump>

Nobody else have this problem? Everybody else has it, but has learned to live with it?

Can anyone reproduce this, or is it just me?